Such filtering devices are used to prevent dirt or other impurities which may be present in a source of fuel from entering a fuel storage tank while the tank is being filled from the fuel source. This is particularly important for fuel storage tanks of motor vehicles since such dirt or impurities can enter the fuel system of the vehicle and block the operation of carburetors, fuel injectors, etc. of the vehicle.
Several problems have been encountered in providing such motor vehicle fuel filtering devices, particularly if the motor vehicle is intended to be operated by unleaded fuel and the filtering device is intended to remain in the vehicle and continue to be effective for successive fueling operations.
With the introduction of unleaded gasoline, for example, the diameter of the gasoline tank inlet aperture of the vehicle has generally been restricted by law to a diameter only slightly larger than the unleaded gasoline pump nozzle in order to prevent entry of a larger diameter leaded gasoline pump nozzle. The body of the filtering device must, therefore, be very thin in order to permit insertion and withdrawal of the unleaded gasoline nozzle from a filtering device previously inserted through this only slightly larger diameter inlet aperture. This will, of course, also be true with leaded gasoline if the leaded gasoline inlet aperture is made only slightly larger than the leaded gasoline pump nozzle.
In addition, the gasoline tank inlet aperture of a motor vehicle is also required by law in many jurisdictions to have a spring loaded cap or barrier closing the aperture, except during nozzle insertion, to reduce the gasoline fumes escaping from the gasoline tank. Consequently, any filtering device which opens this spring loaded cap, and is intended to remain within the gasoline inlet aperture after the filling operation, must likewise have a spring loaded barrier to close its own passageway and reduce the gasoline fumes from escaping therethrough.
Furthermore, the gasoline filling passageways of the vehicle leading to and/or from the actual gasoline tank inlet aperture may assume different lengths and diameters which may be close to the sides or top of an inserted filtering device and thus inhibit the operation of any fume reducing barrier or handle means of the filtering device.